Quick fix: Spread the stitches on your right needle to their full width before stranding the inactive yarn. The float needs to span that full width comfortably to prevent puckering.
What you are seeing
Your stranded colorwork fabric has tight, gathered sections. The wrong-side strands running between colour blocks are short and taut instead of lying flat.
Why it happens
- Not spreading stitches before stranding the inactive yarn
- Catching floats too frequently, pulling them tighter
- Tension tighter in colorwork than plain stockinette
Fix it now
- For existing puckering: wet block aggressively — stretch the fabric while damp and pin to measurements. Floats have hidden slack that blocking redistributes.
- If severe, rip back and re-knit, this time spreading stitches before each float.
- Going forward: before carrying inactive yarn, spread the stitches you just worked to their full width on the right needle. The float should span that width.
Prevent it next time
- Spread stitches wide on right needle before every float
- Catch long floats (longer than 5 stitches) by trapping under working yarn
- Use a larger needle size for colorwork — tension naturally tightens